1. Statement of the Technical Field
The present invention relates generally to circuits that can be physically integrated with elements of structure.
2. Description of the Related Art
Conventional printed circuit board (PCB) technology has been used extensively in designing complex circuitry. PCB's can be manufactured in a variety of two-dimensional planar shapes. Typically, PCB circuitry is incorporated into a system by mounting one or more rigid PCB's to a structure using some sort of mechanical fastener. This method of attaching circuitry to structure can be problematic, particularly when the space available for housing such circuitry is small or awkwardly shaped.
The development of flexible circuits has provided designers with an alternative to PCB circuit construction. A flexible circuit, as its name implies, is not rigid. Rather, thermoplastic, or a thermoset polymer (polyamide), is used as a base material upon which conductors can be etched. Flexible circuitry, because of its inherent ability to bend, can be used in a larger number of environments and spaces than rigid PCB circuitry.
One variety of flexible thermoplastic circuit is the liquid crystal polymer (LCP) film circuit. LCP circuits are constructed using LCP as a substrate. LCP is a type of thermoplastic aromatic polyester that offers several advantages, particularly with respect to traditional polyimide film circuits. For example, LCP circuits exhibit beneficial electrical properties such as a low dielectric constant which facilitates faster electrical signal transfer. Additionally, LCP has very low moisture absorption, typically on the order of 0.02%. Low moisture absorption also facilitates stable high frequency signal and data processing, allowing LCP circuits to be used at frequencies in and around 40 GHz. Accordingly, LCP circuits are suited to a variety of different applications including, but not limited to, high frequency microminiaturization, sensors, antennas, and high speed flip-chip designs.
To date, flexible circuits have been attached to structures using adhesives. The use of adhesives, however, is less than ideal. In particular, if the structural element to which the flexible circuit is attached is subjected to stress, a portion, or all, of the flexible circuit may become detached from the structural element. Further, such configurations typically do not contribute to the overall strength of the structural element to which the flexible circuit is attached. Such is the case as the flexible circuit and the structural element, despite the use of an adhesive, still are essentially separate and distinct components.